My foreman, engine is all stock, no snorkel or anything. Cleaned the carb because it was backfiring and idling fine but when you give it throttle the power isn’t there. Ran great last time I was out about 3 weeks ago. New plug. I’m lost. There is a little rattle in the exhaust, seems to be a new noise. It did always backfire when I went down a hill and let off the throttle. Any help would be great. Thanks